As an important switching element, thin film transistors are one of the most widely used devices in driving circuits. With the continuous development of science and technology, the requirements for flexibility and transparency of the thin film transistors are increasing. At present, the thin film transistors are mainly prepared by conventional photolithography, printing or other technologies, which usually requires multiple alignment operations between patterns of multiple sets of masks or multiple concave/convex plates, and thus undoubtedly increases the complexity of preparation and reduces the precision of preparation. Therefore, researchers have proposed a self-aligned technology at the expense of a reduction in the transparency of devices, that is, a non-transparent gate (e.g., metal or polycrystalline silicon) is used as a photolithographic mask (referring to MUNZENRIEDER N, PETTI L, ZYSSET C et al., Flexible Self-Aligned Amorphous InGaZnO Thin-Film Transistors With Submicrometer Channel Length and a Transit Frequency of 135 MHz [J]. IEEE Transactions on Electron Devices, 2013, 60(9); 2815-2820.), and a back-face exposure method is adopted for obtaining patterns of the source and drain. However, although this technology reduces one procedure for pattern alignment and saves one set of masks or concave/convex plates, the full transparency of electronic devices cannot be realized for the use of the non-transparent gate, and the current requirements for fully-transparent electronic devices cannot be satisfied. As will be understood by those skilled in the art, “fully-transparent” means that the electronic devices and the circuits have a transmittance of more than 80% over the whole visible light range (400 nm to 790 nm).
In addition, flexible thin film transistors fabricated by roll-to-roll printing or other technologies exhibit excellent device performances. So far, many flexible devices having a mobility higher than 30 cm2/Vs and a subthreshold swing less than 100 mV/dec have been reported. However, since polymer substrates are easy to deform, flexible transistor devices fabricated by roll-to-roll printing technologies have a feature size greater than 100 which is much larger than 14 nm achievable on silicon-based devices by the conventional photolithography. This will severely influence the circuit integration and the maximum operating frequency, and greatly hinder the application of flexible electronic devices in the field of integrated circuits and the high frequency field.
Also, in the prior art, the thin film transistors are usually fabricated into thin film transistor arrays. In order to realize the separation of electrodes of different thin film transistors, an additional patterning process is usually required to separate adjacent thin film transistors.